Production of monofilaments



Patented June 15, 1943 UNITED STATES PATENT OFFICE to American Viscose Corporation, Wilminxt Del., a corporation of Delaware No Drawing. Application November 18, 1941,

Serial No. 419,571

19 Claims.

This invention relates to the production of mono-filaments and more particularly to imparting a smooth polished surface thereto. This invention is particularly applicable as a modification of the procedures employed by Heymann in application Ser. No. 413,242, filed October 1, 1941. However, it is not limited thereto as it may also be applied to mono-filaments produced in other ways or even from other materials. It is generally applicable to such unitary filaments as are produced by fusion of thermoplastic filaments by heat alone, without any substantial assistance of swelling agents.

In accordance with application Ser. No. 413,242,

mono-filaments are produced from individual filaments composed of such vinyl resins as thecopolymers of vinyl acetate and vinyl chloride, chlorinated copolymers .of vinyl acetate and vinyl chloride, polyvinyl chloride, and chlorinated polyvinyl chloride which have been stretched during their production. In accordance with that invention, a bundle of the individual filaments is given a certain amount of twist, on the order of a fraction of one turn per-inch up to about turns per inch, and the twisted bundle is heated while it is held in such a manner as to prevent any substantial longitudinal contraction. The amount of twist is preferably not less than 3 turns per inch; higher amounts of twist up to 15 turns per inch yield products having more pliability than those obtained from lower amounts of twist. The heating may be performed by steam, hot air, hot water, or other heated liquids inert with respect,to the vinyl resins, that is, liquids which exert no swelling, softening, or dissolving action upon the resins, such as glycerine, ethylene glycol, or other polyhydric alcohols. A certain amount of shrinkage may be permitted during the heating without interfering with the formationof a mono-filamentary structure. However, any substantial contraction is preferably avoided as the product would then be subject to more permanent elongation upon stretching and would have less tenacity.

The mono-filaments resulting from the procedure of application Ser. No. 413,242 are highly satisfactory from the viewpoint of uniformity of diameter along their length, but in the case of mono-filaments having large diameters, such as would be suitable for making violin strings, they exhibit a certainamount of roughness upon their surface. While this roughness of the mono-filaments is not objectionable for certain P p ses, yet for other purposes, particularly for use as violin-strings, a very smooth and well polished mono-filament is desired to improve wearing and sometimes other qualities, such as tone. The mono-filaments may be polished by suitable abrasive means, such as by pumice powder in olive oil, but it has been found that the results of such a procedure are generally not satisfactory and require an excessive amount of work and time.

In accordance with the present invention, mono-filaments having exceptional smoothness and polish have been obtained by a modification of the direct abrading procedure described above without the necessity of employing excessive amounts of work and time to accomplish the polishing or abrading. In general, the invention contemplates the preliminary treatment of the material inthe form of the filamentary bundle or the mono-filament with a swelling or solvent agent for the resin of which it is constituted. Subsequent to'the drying or evaporation of the swelling or solvent agent and fusion, regardless of the order of these steps, the polishing is performed.

For example, the mono-filaments such as those resulting from'the procedure of application Ser. No. 413,242, may be superficially treated with a swelling agent, and after drying of the monofilaments, they may be polished by means of pumice or other abrasive powder wetted with olive oil or other lubricant. This procedure results in considerable improvement in'the resulting polish of the filament and also in a reduction of both the abrading time and work required.

However, even better results have been obtained by the following alternative "procedure, which is the preferred embodiment, of this invention. This procedure involves a preliminary treatment of the filamentary bundle before 'it is converted to the mono-filament by heat or the heated inert medium, such as air, steam, water, etc. with a solvent or swelling agent for the resin (or other material whatever the case may be) of which the filaments are composed, such as ace-- tone, ethyl acetate, etc., care being taken during this treatment that it is not so drastic as to weaken or to shrink the filaments of which the bundle is composed. The treatment is controlled so that the swelling effect of the solvent agent is mainly limited to the surface of the filaments and it may or may not be but preferably should be sufiiciently drastic to cause the several filaments to adhere to one another as a result of the superficial softening and tackiness of the individual filaments. In any event, however, the intermediate product obtained from this prelimi- The twistedfilamentary bundle is wetted inert with respect to the resin filamentasuch'ashwater, alcohol, etc.

Th preliminarily treated filamentary bundle, after evaporation of the softening or swelling agent, is then subjected to the procedure of application Ser. No. 413,242 for converting it into the mono-filament, or to any other similar procedure adapted to. the particular material of which the filaments are composed for such conversion. While it is preferred that substantially all of the solvent be evaporated from the preliminarily treated bundle of filaments before the conversion into the mono-filament, it is permissible to allow an appreciable amount of such solvent to be evaporated during the first part of the heating step constituting the conversion into the mono-filament. After the mono-filament is obtained in accordance with the preferred procedure, it is polished, such as by means of pumice powder in olive oil. The polishing may be performed by imparting a combined longitudinal peripheral motion to the mono-filament as it is passed between suitable surfaces to which the wetted abrasive powder has been applied, such surfaces being of any desired shape, fiat or curved to conform to the curvature of the mono-filament. If desired, the mono-filament may be drawn past a series of abrasive stones to effect uniform polishing around the entire circumference of the filament.

The procedure in accordance with this invention, particularly the latter alternative procedure, results in a remarkable improvement in the polished surface of the mono-filaments and a remarkable reduction of time and work required to impart such a surface thereto. It is unexpected that the preliminary treatment prior to the conversion into the mono-filament should produce even better results than those obtainable by the procedure in which the solvent is applied to the mono-filament just prior to the abrasive action. The polished string of vinyl resin made in accordance with this invention is considerably more translucent than that obtainable by -polishing the mono-filaments made in accordance wtih Ser. No. 413,242. The product, in general, appears to be much nearer to what may be called a true mono-filament.

As in application Ser. No. 413,242, the terms monofiP and "mono-filament are used in the specification to describe the unitary filament obtained in accordance with the method herein disclosed, it being understood that these expressions are to include not only true monofils but also such structures as have the outward appearances and characteristics practically indicative of substantially true mono-filaments even though special rupturing procedures may indicate that the structures are composed of numerous filaments or fibers not entirely coalesced along their lengths into absolutely true mono-filaments. In this specification also, the expressions "unitary filament used in the claims is to be construed in a correspondingly broad sense to include both true and practical mono-filaments.

bristlesfor brushes, artificial horse hair, etc.

"While a preferred embodiment of the invention disclosed, the description is intended to be illustrative only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the invention as defined by the appended claims.

WhatIclaimis:v

1. In the methodof forming a unitary filament by fusingfa bundle of filaments formed of thermoplastic material and subsequently polishing the surface thereof by abrading, the step of subjecting the filamentary material at a stage of manufacture prior to final polishing by abrading to a superficial treatment with. a swelling agent therefor and to a substantially complete drying thereof.

2. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments by fusion thereof and subsequently polishing the surface by abrading, the step of subjecting the filamentary resin material to be polished at a stage of manufacture prior to final polishing by abrading, to a superficial treatment with a swelling agent therefor and to a substantially complete drying thereof.

3, In the method of forming a unitary filament from a filamentary bundle, the steps of effecting fusion of said filamentary bundle into a unitary filament, superficially treating said filament with a swelling agent therefor, evaporating substantially all of the swelling agent therefrom, and polishing the surface thereof by abrading.

4. In the method of forming a unitary filament from a filamentary bundle, the steps comprising superficially treating said filamentary bundle with a swelling agent for the material of which the filaments are composed, effecting fusion of said filamentary bundle into a unitary filament substantially free of swelling agent, and polishing the surface therepf by abrading.

5. In the method of forming a unitary filament from a filamentary bundle, the steps of superficially treating said bundle with a swelling agent for the material of which the filaments are composed, and after evaporation of substantially all of said swelling agent from said bundle, effecting fusion of said filamentary bundle into a unitary filament by heating said bundle,

6. In the method of forming a unitary filament from a filamentary bundle, the steps of superficially treating said bundle with a swelling agent for the material of which the filaments are composed, and after evaporation of substantially all of said swelling agent from said bundle,'eflecting fusion of said filamentary bundle into a unitary filament by heating said bundle and subsequently Polishing the surface thereof.

'7. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments stretched in excess of 50%, the steps of twisting said bundle, superficially treating said twisted bundle with a swelling agent therefor, and effecting fusion of said filamentary material into a unitary filament by heating said to evaporate, therefrom,

bundle while preventing any substantially longitudinal contraction thereof.

8. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments stretched in excess of 50%, the

steps of twisting said bundle, effecting fusion of said filamentary material into a unitary filament by heating said bundle while preventing any substantial longitudinal contraction thereof, and superficially treating said unitary filament with a swelling agent for the material of which it is composed. l

9. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments stretched in excess of 50%, the steps of twisting said bundle, effecting fusion of said filamentary material into a unitary filament by heating said bundle while preventing any substantial longitudinal contraction thereof,

superficially treating said filament wltha swelling agent for said vinyl resin, and polishing the surface thereof after removal of substantially all of said swelling agent.

10. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments stretched in excess of 50%,

the steps of twisting said bundle, superficially treating said twisted bundle with a swelling agent for the resin thereof, permitting substantially all of said swelling agent to evaporate, effecting fusion of said filamentary material into a unitary filament by heating said bundle while preventing any substantial longitudinal contraction thereof, and polishing the surface thereof.

11. In the method of forming a unitary filament from a bundle comprising thermoplastic viny1 resin filaments having a stretch in the order of about 75% to 1000% the steps of imparting a twist of the order of a fraction of one turn per inch to fifteen turns per inch to said bundle superficially treating said twisted bundle with a swelling agent for the resin thereof, effecting fusion of said bundle into a unitary filament by heating said bundle in the presence of an inert fluid While preventing any substantial longitudinal contraction thereof, and polishing the surface thereof.

superficially treating said twisted bundle with a swelling agent for the resin thereof, causing or permitting substantially all of said swelling agent then effecting fusion of said bundle to a unitary filament by heating said bundle in the presence of an inert fluid while preventing any substantial longitudinal contraction thereof, and subsequently polishing the surface of the unitary filament.

13. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic viny1 resin polymer having a stretch in excess of 50%, the steps of imparting twist to said bundle, superficially treating said twisted bundle with a swelling agent for the resin thereof to effect a preliminary tacking together of said filaments without effecting shrinkage thereof and without destroying the external appearance tothe effect that the bundle is still made up of a plurality of individual filaments, and effecting fusion of said bimdle into a unitary filament by heating said bundle in an inert fluid while preventing any substantial longitudinal contraction thereof, and subsequently polishing the surface of the unitary filament.

'14.'In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of the steps of imparting twist to said bundle, superficially treatingsaid twisted bundle with a swelling agent for the resin thereof to effect a preliminary tacking together of said filaments without effecting shrinkage thereof and without destroying the external appearance to the effect that the bundle is still made up of a plurality of individual filaments, effecting fusion of said bundle into a unitary filament by heating said bundle in, an inert fluid while'preventing any substantial longitudinal contraction thereof, and

preliminary tacking together of said filaments without effecting shrinkage thereof and without destroying the external appearance to the effect that the bundle is still made up of a plurality of individual filaments, and effecting .fusion 'of said bundle into a unitary filament by heating said bundle in an inert fiuid while preventing any substantial longitudinal contraction thereof and polishing the surface thereof.

16. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic vinyl polymer having a stretch in excessof 50%, the steps of imparting a twist of said bundle, superficially treating said bundle with a swelling agent for the resin thereof, winding said twisted bundle in the form of a package after evaporation of substantially all of the swell-' ing agent therefrom, effecting fusion of said a bundle into a unitary filament by heating said package in the presence of an inert fluid.

17. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%,

the steps of imparting a twist of saidbundle,

. vinyl acetate having a stretch in excess of 50%,

the steps of imparting a twist to said bundle, superficially treating said bundle with a swelling agent for the resin thereof, winding said twisted bundle in the form of a package after evaporation of substantially all of the swelling agent therefrom, effecting fusion of said bundle into a unitary filament by heating said package in the presence of an inert fluid and polishing the surface of said filament.

19. In the method of forming a unitary filament from a bundle'comprising filaments of a thermoplastic after-chlorinated copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%, .the steps of imparting a. twist bundle into a unitary filament by heating said to said bundle, superficially treating said bundle package in the presence of an inert fluid and with a swelling agent for. the resin thereof, windsubsequently polishing the surface of said filaing said twisted bundle in the form of a package ment.

after evaporation of substantially all of the swell-F 5 WAYNE I. NEWHARD. ing agent therefrom, efiecting fusion of said 

